Partitioning, Translocation Pathways and Environmental Risk Evaluation of Selected Polychlorinated Biphenyls and Pesticides

Abstract

Degradation-resistant chemical contaminants of health concern such as dichlorodiphenyltrichloroethane (DDT) pesticides and polychlorinated biphenyls (PCBs) in the environment are redistributed between different environmental compartments, where they partition between biotic heterotrophic routes and abiotic features (water and immobile soil components). Their fate and the potential risk they pose is a function of translocation, interaction, environmental behavior, and bio-translation/activities. In this study, the partitioning, translocation, bio-translation pathways of 3-DDT and 6-PCB congeners in dosed soils cultured root and leaf vegetables were investigated to predict their soil–vegetable mobility, depuration, and exposure risk. Results showed that PCB_110 and PCB_180 were the least and highest PCBs concentrated in both the leaf and root vegetables. The variations in the 3-DDT and 6-PCB concentrations in the leaf and root vegetables may be attributed to differences in their solubility and partitioning. Total residual mass fraction 3-DDT taken up by the leaf and root vegetables indicated time-dependent preferentiality in pesticide-type vascular tissue translocation to the vegetables. Mann–Whitney non-parametric test showed evidence of spatial variations in levels of the 3-DDT and 6-PCBs across the farmland; however, the variations in the distribution were not significant (PFML1–FML6 <<Pstat). Risk factors for 3-PCBs and 3-DDT tend to 1(f < 1.0), while that for PCBs_149, 153, and _180 were far less than 0.4 (<1.0). It is therefore uncertain that any immediate health risks could arise from exposure to vegetables containing such congener levels. Continuous exposure to an extrapolated estimate of 25% vegetable population has a 20 ± 10% probability of leading to undesirable chronic effects.